The present invention is based on an apparatus for influencing the operating state of an electronic device using a transponder.
German Published Patent Application No. 295 14 056 describes device for protecting an audio device from unauthorized use in which, after removal of a movable part detachably joined to the audio device, operation of the audio device is interrupted and is not enabled again, after the movable part has been put back, until an access code that is accepted as authorized by the audio device is emitted from the transponder arranged for that purpose in the movable part.
Also known from the field of entertainment electronics, for the operation of, for example, television sets, video recorders, and audio systems, are infrared remote controllers with which at least a portion of the available functions of the relevant device can be remotely controlled.
The apparatus according to the present invention has the advantage that a movable part equipped with a transponder can be used not only as a simple theft protection system but also as a remote controller for controlling electronic devices.
The apparatus according to the present invention has the advantage, as compared to known infrared remote controllers, that because a transponder is used, batteries for supplying energy to the movable part are superfluous. This results in a reduction in the weight and volume of the movable part, and also eliminates the need to dispose of environmentally incompatible used batteries.
A further advantage of the proposed approach is that precise alignment of the movable part on the device-mounted receiver is not necessary, since, in contrast to known infrared remote controllers, the transfer of electromagnetic waves emitted by the movable part to the receiver functions even in the absence of visual contact.
In addition, the insensitivity of the apparatus to incident light prevents improper operation, as a consequence of stray incident light, of the device being operated.
It is furthermore advantageous that the oscillation exciting the transponder, and the transmitted signal of the transponder, are emitted in continuous alternation. In this fashion, the exciting oscillation and the transmitted signal can be transmitted on the same transmission frequency, so that the oscillating circuits in both the receiver and the transponder can be optimized for the transmission and reception of the electromagnetic oscillations on the same frequency.
In terms of the specifications applicable to the electromagnetic compatibility of electronic systems, it is advantageous to match the transmission frequency and transmission output to one another so that propagation of the oscillations which excite the transponder or are emitted by the transponder is confined to the premises in which the device to be operated is located.